Float switch apparatus

ABSTRACT

The present invention relates to float switch apparatus having unusual stability. Broadly, the float switch apparatus of the present invention comprises a buoyant lever arm having a fulcrum at one end thereof comprising a transverse shaft. Said shaft is pivotally associated with an appropriate mount. A switch means, responsive to angular deflection, is positioned within the lever arm and the conductor wires associated with said switch are routed through the transverse shaft and exit said shaft through radial apertures provided therein. Said wires then form a helical coil about said shaft and are affixed to the mount. Additionally, for greatest efficiency and stability, it is much preferred that at least the bottom, and most preferably also the top, surfaces of the lever arm be tapered.

United States Patent [72] Inventor Clinton Rule Beverly Farms, Mass. [21] AppLNo. 706,886 [22] Filed Feb.20,1968 {45] Patented .july13,l971 [73] Assignee Rule Marinmlne.

Beverly Farms, Mass.

[54] FLOAT SWITCH APPARATUS 7 Claims, 2 Drawing Figs.

[52] U.S.Cl 200/848, 73/313 [51] lnt.Cl ..H0lh35/l8 [50] FieldofSearch 200/84, 84.2;73/313 5 6] References Cited UNITED STATES PATENTS 2,690,484 9/1954 Buchtenkirch ZOO/84.3 1,941,815 1/1934 Ringstrom 200/84.2UX 2,136,220 11/1938 Shepherd 200/152X 3,183,323 4/1965 Englesson 200/84.2UX 2,055,501 9/1936 Morrow 200/84.2UX

2,580,759 l/1952 Gille ZOO/84.2 UX

2,903,532 9/1959 Gonetzm. 200/84 3,309,687 4/1967 ZOO/84.2 UX FOREIGN PATENTS 6,805 H1905 Great firltainsunimuu. 73/317 Primary Examiner ljavid Smith, Jr. Attorney william N. Anastos transverse shaft and exit said shaft through radial apertures provided therein. Said wires then form a helical coil about said shaft and are affixed to the mount. Additionally, for greatest efficiency and stability, it is much preferred that at least the bottom, and most preferably also the top, surfaces of the lever arm be tapered.

PATENTEU JUL 1 3 IQYI SHEET 2 BF 2 (STAGE 8) 8 (STAGE A) FIG. 2

FLOAT SWITCH APPARATUS are normally routed through the lever arm in any convenient manner and, ofcourse, eventually communicate with the elecoperated thereby. The shapes of the lever arms utilized in prior art float switches have been subject to wide variation. Unfortunately, however, the float switches of the prior art have most frequently not achieved the full measure of their potential in marine applications, due, in large measure, to a general lack of stability and/or responsiveness under the marine environment. Specifically, prior art switches reduced.

It is a principal object of the present invention to provide a novel float switch device having unusually stable operating characteristics.

It is another object of the present invention to provide a novel float switch which have an unusually long operating life and which is constructed so as to prevent electrical arcing.

It is another object of the present invention to provide a novel float switch wherein the switch mechanism is contained within the lever arm for maximum compactness.

Other objects and advantages of the present invention will in part be obvious and will in part appear hereinafter.

A better understanding of the apparatus of the invention can be had by reference to the drawings forming part hereof wherein:

FIG. 1 is a partially sectionalized isometric schematic view of the float switch apparatus of the instant invention.

FIG. 2 comprises a schematic side elevation of the apparatus of F 1G. 1 in two representative stages of operation.

Referring now to the drawings, buoyant lever arm 1 has a relationship by apertures 4 of mount means 5 thereby establishing pivotal relationship of said lever arm relative to said mount means. The electrical components of the float switch comprise a switch device 7 responsive to angular and wire conductors 9 in electrical communication with said switch device. Said switch device 7 can be conveniently mounted within the lever arm by means ofa suitable bedding compound 11.

While any electrical switch responsive to angular displacement is suitable, I much prefer for the sake of simplicity, reliability, nonarcing characteristics, and efliciency, those switch devices characterized by an insulative capsule 6 which contains a globule ofa liquid electrolyte therein and which has at one end thereof contact leads. in operation, referring now specifically to FIG. 2, liquid electrolyte globule 8 remains out purposes of the present specification the general term, "mercury switch, encompasses the preferred switch device. Needless to say, however, any electrolyte or conductive material such as small metal balls or metal powder can be utilized although liquid electrolytes, and especially mercury, are preferred.

A critical feature of the invention resides in the manner by which conductor wires 9 whichcommunicate with said switch present invention, the routing is achieved in a manner which allows the level arm to move upwardly and downwardly with a minimum of interference or drag. Specifically, in accordance with the present invention, said wires are routed through shaft 3 and are exited therefrom through radial apertures 13. The wires are then wound about their respective shafts for at least one-half turn and most preferably at least one whole turn so as to form coils l9 and 20, preferably in such a direction that any resistance to motion ofthe lever arm will occur when the float is rising and so that assistance to motion of the lever arm is provided in the downwardly direction. The so coiled conductor wires are then firmly affixed to mount 5 by any suitable means. The anchoring or fixing of the conductor wires can be achieved in any suitable manner such as by routing said wires through holes 15 provided in floor 17 of mount 5 and knotting each of the wires at the exit sides of their respective holes; or alternatively, knotting the conductor wires together below floor 17. Still another method for anchoring which I have found particularly advantageous comprises applying a suitable cement at holes 15. With respect to said sealing function, it should be noted that it is most important in accordance with the present invention that lever arm I be leakproof. In the particular apparatus shown in FIGS. 1 and 2, the only pathways available for leakage into said arm are through apertures 13, and ends 21 and 23 of shaft 3. Obviously, said potential leakage pathways should be blocked, for instance by plugging of said apertures with a suitable sealant.

ln any case, optimum adjustment of the length of the conductor wire coils 19 can generally be determined during assembly of the apparatus by maintaining lever arm 1 in its upwardmost intended operating positions and taking up on each of the conductor wires sufficiently to leave just a little slack in coils l9 and 20. The conductor wires may then be anchored to the mount means thereby achieving sufficient coil diameter to allow free deflection of lever arm 1 thereby providing excellent responsiveness and reliability to the present switch. The precise reasons why the coils result in superior operational staunderstood. However, it is believed that the with substantial benefits, it is nevertheless generally preferred to employ conductor wires comprising at least about three strands, thereby even further alleviating the possibility of undesirable stress concentrations occuring within the conductors during operations.

Another important feature of the apparatus of the present invention which results in even further stability benefits, resides in the particular shape of lower and upper surfaces 30 and 32 respectively of lever arm 1. Specifically, it has been found that bottom surface 30 should be tapered toward end 36 and shaped so that surface 31 of capsule 6 and surface 30 are parallel. Thus a rectangular lever arm 1 would not be very efficient as relates to buoyancy, and moreover, a rectangular arm would have to be mounted higher in order to allow arm I to swing through any given arc. The net result therefore of utilizing a rectangular arm would be a switch which would require a deeper ambient water level for activation and which would leave more water at shut off. When, however, bottom surface 30 is tapered, it then becomes most desirable for top surface 32 to be tapered also in order to maintain a proper weight relationship for lever arm 1. The extent of tapering is not critical but tapering at angles between 5 and 25 has been found to be effective.

Another very important factor in the present invention is the shape of capsule 6 comprising switch 7. Said capsule preferably has an angle therein of between and 75, about 25 having been found to be excellent. The angle is most important in order that the switch open and close at substantially different liquid levels. Thus the shifting of the electrolyte from one end to the other in an angled capsule affects the "time delay" response and therefore the stability of the present switch. It is important therefore in accordance with the present invention that the electrolyte or conductive material move from substantially one extremity of capsule 6 to the other, shifting dramatically the location of the center of gravity and assuring extended time delay coupled with small size and low cost.

Still another feature which results in greater sensitivity and stability during operations of the present switch resides in the presence of hairline ridges 22 about the ends of shaft 3. It is believed that these ridges serve to minimize the contact area between the shaft ends and the interior surfaces of mount walls 25 thereby effectively reducing the frictional forces that are developed. Also, apertures 4 should have a circular crosssectional shape in order to provide only slight contact and reduce frictional drag.

Still another feature of the present float switch apparatus resides in the positioning on mount 5 and/or on lever arm 1 of stop means which prevent lever arm 1 from rising to the vertical position. In FIG. 1, small projections 40 on the surface of mount 5 and arm 1 which are positioned so as to collide with one another when arm 1 describes an angle of about 75 from the horizontal serve as the stop means,

Materials of construction which are suitable for the nonelectrical components of the float switch apparatus of the present invention are obviously subject to wide variation. Various metals such as copper, brass, steel, etc, are, of course, suitable. However, the structural members of float switches in general are normally well-suited to production by thermoplastic molding techniques. Thus, for purposes of construction ease and in order to readily provide a generally inert character, polymeric resins such as polyethylenes, polyamides, polystyrenes, polycarbonates, and the like, are much preferred. In particular, polymeric resins of the polyacetal type (-OCH have been found to be exceptionally useful materials of construction. It should be remembered that lever arm 1 must be as light as possible in order to float readily (have a high ratio of buoyancy to weight) and yet heavy enough to be sure of rotating downwardly against frictional resistance and the tendency to remain up because of sludge or thick grease accumulations.

Obviously, many changes can be made in the above description and the specific disclosures in the drawings without departing from the scope and intent of the invention. For instance, while the float switch apparatus specifically described herein operates in such a manner as to make contact upon an upward angular deflection ofthe lever arm, clearly the making of contact can also be effected upon downward deflection thereof such as by altering the position of switch device 7 by I What I claim is:

l. A novel float switch comprising a buoyant lever arm having a fulcrum at one end thereof comprising a transverse shaft pivotally associated with a mount, said lever arm the bottom surface of which tapered toward the free end thereof containing therein and in fixed relationship with respect thereto a switch means responsive to angular deflection said switch means comprising an airtight capsule having an angle in at least the bottom wall thereof of between about 15 and about 75, and containing a small amount of an electrolyte and contact wires located at one end thereof, said contact wires being connected to leads which exit said lever arm through radial openings in said transverse shaft and then loop around said transverse shaft at least one-half turn.

2. The switch of claim 1 wherein the bottom surface of the capsule at the end where the contact wires are located is parallel to the tapered bottom surface of said lever arm.

3. The switch of claim 1 wherein the top surface of said arm is also tapered toward the free end thereof.

4. The float switch of claim 1 wherein said contact wires after looping around said shaft at least one-half turn pass through said mount and are secured.

5. The float switch of claim 1 wherein said transverse shaft and said mount are in contact only through hairline ridges.

6. The float switch of claim 1 wherein the electrolyte comprises mercury.

7. The float switch of claim 1 wherein stop means are provided which prevent said level arm from rising to the vertical position. 

1. A novel float switch comprising a buoyant lever arm having a fulcrum at one end thereof comprising a transverse shaft pivotally associated with a mount, said lever arm the bottom surface of which tapered toward the free end thereof containing therein and in fixed relationship with respect thereto a switch means responsive to angular deflection said switch means comprising an airtight capsule having an angle in at least the bottom wall thereof of between about 15* and about 75*, and containing a small amount of an electrolyte and contact wires located at one end thereof, said contact wires being connected to leads which exit said lever arm through radial openings in said transverse shaft and then loop around said transverse shaft at least one-half turn.
 2. The switch of claim 1 wherein the bottom surface of the capsule at the end where the contact wires are located is parallel to the tapered bottom surface of said lever arm.
 3. The switch of claim 1 wherein the top surface of said arm is also tapered toward the free end thereof.
 4. The float switch of claim 1 wherein said contact wires after looping around said shaft at least one-half turn pass through said mount and are secured.
 5. The float switch of claim 1 wherein said transverse shaft and said mount are in contact only through hairline ridges.
 6. The float switch of claim 1 wherein the electrolyte comprises mercury.
 7. The float switch of claim 1 wherein stop means are provided which prevent said level arm from rising to the vertical position. 